Health; Personal Health

By Jane E. Brody

Published: March 24, 1988

If you were among the unfortunate victims of the latest strain of influenza or the mysterious virus that has been prostrating people for up to seven days, you may have considered yourself recovered when the virus retreated, enabling you to return to your usual activities. But in addition to the expected setbacks of a debilitating illness, your body must now also recover from the effects of the treatment: bed rest.

Chances are that while you languished with aches and fever you gave little thought to what the days in bed were doing to your body. If you did know, however, you could plan a more intelligent return to normal activity and better appreciate the risks of trying to do too much too soon.

Understanding the effects of bed rest and initiating activity to counter them can also help patients in hospitals and nursing homes, where many patients' problems are related to the hours they spend in bed.

In the January issue of The American Journal of Nursing, Dr. Marilyn Rubin pointed out that while a night's rest in bed after a long, hard day usually leaves one refreshed, forced bed rest caused by illness or injury can have the opposite effect.

Researchers have estimated that the functional losses after three weeks of total bed rest roughly equal to the effects of 30 years of aging. While the effects of aging may be largely irreversible, the effects of bed rest can almost always be overcome.

The major effects are related to the loss of gravity's pull on your body. As Dr. Rubin explained, when you stand upright, the body fights gravity in ''a most helpful way.'' Your skeletal muscles contract, exerting pressure against veins and lymph vessels, which keeps fluid from pooling in your legs and feet. The antigravitational effort also makes muscle cells more robust and makes the bones stronger because muscle movement against gravity favors calcium deposition in the bones.

But when the mattress is holding you up, your skeletal muscles lose tone.

''After just three days, a person on bed rest loses plasma and calcium, secretes less gastric juice, has less blood flowing through the calves and shows some impairment of glucose tolerance,'' wrote Dr. Rubin, who is a professor of nursing and director of research at St. Louis University's School of Nursing.

System by system, these are among the major effects of bed rest:

Shifts in Body Fluids. You start losing more body fluid than usual the first day, with a loss of about 20 ounces by the second day. This fluid loss is a major factor in the temporary but often dramatic weight loss that can occur in an illness. Along with the lost fluid, sodium and chloride (the ions of salt) are lost immediately. More prolonged bed rest also causes a loss of potassium.

While lying down, there is a shift in blood volume, with blood leaving the legs and pooling in the trunk and head. The mucous membranes in your nose may swell, causing nasal congestion.

Changes in Blood. You may already be aware of the increased risk of blood clots associated with bed rest. That is why hospital patients are given elasticized hosiery, which helps squeeze leg veins the way the muscles do when you stand. After eight days in bed, blood clots faster than usual. The most likely cause of clots is compression of the vessels in the lower legs by the weight of the legs on the bed.

The pressure exerted on certain areas of the body can also cause bedsores. These result when someone in bed does not move or is not shifted frequently. The flow of blood through the tiny blood vessels in the skin can be blocked, causing some cells to die. Some patients eventually develop sores, or skin ulcers, which can progress to a wider area.

Heart and Lung Effects. When you are lying on your back, your lungs change position. Combined with the increased pressure of the abdomen against the diaphragm, this change makes it more difficult to breathe. After three weeks of bed rest, your lungs take in about 26 percent less oxygen. The impaired gas exchange can contribute to the fatigue associated with bed rest. Gas exchange is enhanced if you can lie on your side, switching sides from time to time, instead of on your back.

Hormonal Effects. The usual daily cycles of hormonal release change in prolonged bed rest. After one week, the peak release of epinephrine, a hormone secreted by the adrenal glands, occurs in the afternoon instead of early morning. Changes also occur in the secretion cycles of insulin, growth hormone, thyroid hormones and aldosterone, a hormone that regulates salt levels in the body.

Levels of the male sex hormone, androgen, markedly drop in response to bed rest. Insulin secretion also declines within three days, impairing the body's ability to process sugar.

Calcium and Bone Changes. The well-known calcium losses in astronauts dramatically illustrate the devastating effects on bone of a lack of gravity. After two to four days in bed, the body starts losing calcium. Fewer new bone cells form and more old bone cells are destroyed. In bed rest, there is as much as a 10-fold increase in the loss of minerals like calcium and phosphorus from the central part of the bones.